Wireless communication systems are widely deployed to provide, for example, a broad range of voice and data-related services. Typical wireless communication systems consist of multiple-access communication networks that allow users to share common network resources. Examples of these networks are time division multiple access (“TDMA”) systems, code division multiple access (“CDMA”) systems, single-carrier frequency division multiple access (“SC-FDMA”) systems, orthogonal frequency division multiple access (“OFDMA”) systems, or other like systems. An OFDMA system is adopted by various technology standards such as evolved universal terrestrial radio access (“E-UTRA”), Wi-Fi, worldwide interoperability for microwave access (“WiMAX”), ultra mobile broadband (“UMB”), and other similar systems. Further, the implementations of these systems are described by specifications developed by various standards bodies such as the third generation partnership project (“3GPP”) and 3GPP2.
As wireless communication systems evolve, more advanced network equipment is introduced that provide improved features, functionality, and performance. A representation of such advanced network equipment may also be referred to as long-term evolution (“LTE”) equipment or long-term evolution advanced (“LTE-A”) equipment. LTE is the next step in the evolution of high-speed packet access (“HSPA”) with higher average and peak data throughput rates, lower latency and a better user experience especially in high-demand urban areas. LTE accomplishes this higher performance with the use of broader spectrum bandwidth, OFDMA and SC-FDMA air interfaces, and advanced antenna methods. Uplink (“UL”) refers to communication from a wireless device to a node. Downlink (“DL”) refers to communication from a node to a wireless device. A radio access network (“RAN”) is the infrastructure required to deliver wireless communication services, including access to the Internet. The RAN can manage a broad range of tasks for each user, including access, roaming, connection to the public switched telephone network (“PSTN”) and the Internet, and quality of service (“QoS”) management for data connections.
In a wireless communication system, wireless devices travel through a wireless coverage area while communicating with other hosts either inside a wireless domain or outside in a wired domain. Any wired or wireless host that wishes to communicate using the Internet protocol (“IP”) must be assigned an IP address that can be used to distinguish itself from other hosts. The Internet protocol is used to communicate data across a packet-switched network. The Internet protocol works by exchanging pieces of information called packets. A packet is a sequence of bytes and consists of a header followed by a body. The header describes the packet's source and destination and, optionally, the routers to use for forwarding until it arrives at its final destination. The body contains the data in which the source node is sending.
The Internet Protocol also routes data packets between networks and IP addresses are used to specify the locations of source and destination nodes in the topology of the routing system. The IP address is a numerical identifier that is assigned to devices participating in a network, which uses the Internet protocol to communicate between nodes. Further, the IP address assigned to a host has topological significance in the wired world, meaning that the address can be used to locate the point where the host is physically attached to the network. A router is responsible for forwarding packets to a host and uses the IP address to find a routing table entry that defines the next hop along the path to the attachment point associated with the IP address used by the host. The information in a routing table is quasi-static meaning that a router assumes that an attachment point cannot change unless there is a change in network topology caused by, for instance, a link failure. By contrast, the IP address assigned to a wireless device in a wireless communication system may not be related to the point where the host is attached to the network. In particular, a wireless device can communicate with different access points as it travels through a wireless domain.
In a wireless communication system, a multiple-homed wireless device may have simultaneous connections to multiple radio access networks. In this case, an IP address must be assigned to the wireless device for each access network. Unfortunately, Internet protocols do not provide a generic mechanism to relate such IP addresses to the same wireless device. Therefore, each IP address represents a different end point from the routing perspective of the IP-based network.
When a wireless device is exchanging information with a remote corresponding node (“RCN”) using a protocol such as the transmission control protocol (“TCP”), the end points of a packet flow are tied to the IP addresses used by the wireless device and the RCN when the exchange was initiated. Due to network congestion, traffic load balancing, or other unpredictable network behavior, IP packets can be lost, duplicated, or delivered out of order. TCP detects and solves problems associated with lost, duplicated, or out of order IP packets. Once the TCP receiver has successfully re-assembled the data originally transmitted, it passes the data to the application program. If the wireless device wishes to use a different IP address such as to move to a radio access network (“RAN”) with a better signal, the TCP connection is broken.
Technologies such as Mobile IP have been used to solve this problem but they incur tunneling and signaling overheads, produce sub-optimum triangular forwarding paths, have limited support for multi-homed wireless devices, and result in considerable delay when transitioning between access points. Mobile IP is an Internet engineering task force (“IETF”) standard communications protocol that is designed to allow wireless devices to move from one network to another while maintaining a permanent IP address. For an overview of Mobile IP, see Gundavelli et al., Proxy Mobile IPv6, RFC 5213, August 2008; Johnson et al., Mobility Support in IPv6, RFC 3775, June 2004.; or Perkins, IP Mobility Support for IPv4, RFC 3344, August 2002.
When a wireless device is attempting to exchange information with another wireless device within a heterogeneous environment, the problem is compounded due to difficulties in obtaining the IP address assigned to the other wireless device and in keeping information exchanges alive in the face of handovers by either wireless device that result in a change of IP address. A handover, which is also referred to as a handoff, refers to the process of transferring an ongoing voice call or data session from one channel connected to a radio access network to another channel connected to the same or different radio access network.
A packet flow, which is also referred to as traffic flow or network flow, is a sequence of packets exchanged between a wireless device and an RCN. The packet flow occurs when the information exchanged between a wireless device and an RCN is too large to fit into a single packet and is, therefore, segmented into a plurality of packets either by the source of the information such as a web server or cache server or by an intermediate transit point such as a wireless gateway or access point.
The packet flow should be tied to the information being exchanged and not to the IP address of the communicating end points as is the case with TCP. For further information on packet flow, see Meyer et al., Report from the IAB Workshop on Routing and Addressing, RFC 4984, September 2007.
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